Sintered carbide compositions and method of making the same



y 0, 1956 w. w. WELLBORN 2,753,621

SINTERED CARBIDE COMPOSITIONS AND METHOD OF MAKING THE SAME Filed Feb. 11, 1955 Fig.4

INVEN TOR. William W. Wei/barn BY yu wfl flm H/ ATTORNEY United States Patent SINTERED CARBIDE COMPOSITIONS AND METHOD OF MAKING THE SAME William W. Wellborn, Baldwin Borough, Pa., assignor to Firth Sterling, Inc., Pittsburgh, Pa., a corporation of Pennsylvania Application February 11, 1953, Serial No. 336,324

11 Claims. (Cl. 29-182.7)

This invention relates to sintered carbide compositions and to a method of making the same. It relates more particularly to sintered chromium carbide compositions containing two different chromium carbides and one or more binder metals such as nickel or cobalt. The composition preferably contains a small proportion of one or more grain refining elements such as copper or tungsten carbide. The proportions of the various ingredients are such that the coefficient of expansion of the sintered carbide composition in the temperature range of 32 F. to 576 F. is substantially the same as that of steel, i. e., 6.3 inches per inch per F.

There are many uses for sintered carbide compositions which have coefiicients of expansion substantially equal to that of steel. Such compositions are desirable due to their strength, hardness and wear-resisting qualities, but most of them have coefiicients of expansion which differ substantially from that of steel. Sintered carbide compositions according to the present invention, since they have a coefiicient of expansion substantially equal to that of steel, find particular application as gauge blocks for measuring steel at different temperatures. They also are desirable for many other uses, for example, as sealing rings for pumps and for bearings where the sintered carbide composition is closely associated with a steel element and it is necessary in order to maintain the desired fit to have the sintered carbide composition and the steel element expand and contract substantially equally.

The accompanying drawings illustrate in a diagrammatic manner a gauge block and a method of making it.

Figure 1 is a plan view of the gauge block,

Figure 2 is a side elevation thereof,

Figure 3 is an end elevation thereof, and

Figure 4 is a side elevation of a billet pressed from powder and given a preliminary sintering treatment, the figure illustrating how the billet is severed into a plurality of gauge blocks.

My sintered carbide composition contains by weight about 40% to 60% CraCz, about to 45% Cr4C, the proportion of CrsCz to CrtC being between 1:1 and 7:3, the total of said carbides being between about 86% and 90%, and about 10% to 12% nickel or cobalt, or both, used as binder metals. In the specification and claims, wherever percentages or proportions are given, they mean percentages or proportions by weight, unless otherwise specified. The preferred binder metal is nickel. The composition preferably, although not necessarily, contains a small amount of one or more grain refining elements such as copper or tungsten carbide. Copper is much preferred over tungsten carbide as a grain refining element. Where copper is used, it is employed in an amount from about 0.5% to 2.0% of the composition. Where tungsten carbide is used, it is employed in an 2,753,621 Patented July 10, 1956 ice amount between about 0.5% and 3.0% of the composition.

A preferred composition is:

following manner.

Mix No. 1 is made by mixing CrzOs and carbon in such proportions that, when reacted, it forms CraCz according to Reaction 1.

REACTION 1 Mix No. 2 is made by mixing CrzOs and carbon in such proportions that, when reacted, it forms CI4C according to Reaction 2.

REACTION 2 Mixes 1 and 2 are heated separately in a hydrogen furnace to carry out Reactions 1 and 2, employing, for example, a temperature of 2700 F. for two hours. The CrsCz and Cr4C so produced are crushed and mixed together and the mixture is then ball milled for a period of, say, 48 hours in order to intimately mix the carbides and reduce them to fine particles. The nickel or cobalt, or both, are then added and if the composition is to contain copper or tungsten carbide, they are added and the mixture is ball milled for a period of, say, 72 hours. A pressing lubricant, for example, parafin, in a small amount, say 1 /z%, is added to the powder mixture. The mixture is then pressed into a billet under a pressure which may be 10 tons per square inch and is then given a preliminary sintering at a temperature of, say, 1300 F. in hydrogen for one hour. The billet which has been given a preliminary sintering is then severed into a plurality of bodies and the bodies are then given a final sintering at a temperature higher than the preliminary sintering in order to produce strong articles, the temperature employed being, say, 2700" F. to 2800 F. for a period of 30 minutes to minutes, the sintering being carried out in a hydrogen furnace. Thereafter, the article, if desired, is diamond lapped or otherwise ground or finished to accurate dimensions.

The following example further illustrates my invention:

Example 18.625 lbs. of CrzOs and 6.375 lbs. of carbon were mixed to form mix No. 1. 15.6 lbs. of C1'2O3 and 4.40 lbs. of carbon were mixed to form mix No. 2. The two mixes were heated separately in a hydrogen furnace at 2700" F. for two hours. Mix No. 1, when reacted according to Reaction No. 1, produced 12.25 lbs. of Cr3C2 containing 13.33% of carbon. Mix No. 2, when reacted according to Reaction No. 2, produced 8.96 lbs. of CmC containing 5.45% of carbon.

The Cr3C2 and CI'4C were crushed, mixed together and ball milled for 48 hours. The mixture contained about 57% Cr3C2 and 43% Cr4C. Nickel and copper in amounts to provide 11% nickel and 1% copper were added to the carbides and the mixture was ball milled for 72 hours. Thereafter, 1 /2% of paraflin dissolved in a solvent was added to the mixture. The mixture was then further processed to form gauge blocks such as illustrated in Figures, 1,-3.

Each of the gauge blocks has a length L, a width W and a thickness T. The powder was pressed into a billet 2 as shown in Figure 4, this billet having a length many times greater than the thickness T of the gauge blocks to be formed therefrom. In carrying out the pressing operation, pressure was exerted in the direction of the longitudinal axis of the billet as indicated by. the, arrow. 3. The pressure mounted to 10 tons per square inch. The compressed billet 2 was then subjected toa preliminary sintering in a hydrogen furnace at a temperature of 1300" F. for one hour so as to produce a coherent mass which could be handled and shaped but which was not so hard. as to make shaping difli'cult. The billet was then sawed transversely into a plurality of gauge blocks by sawing along the lines 4. Thereafter, the gauge blocks were subjected to a final sintering in a hydrogen'furnace'at a temperature of 2700 F.2800 F. for one hour.

Gauge blocks, or other articles madein the manner described, may thenbediamond lapped-or otherwiseground and finished to accurate dimensions.

The article produced accordingto the example had a coeflicient of expansion in the temperature range of 32 F. to 576 F. of 6.3 l inches per inch per F., a Rockwell A hardness of 90 and a transverse breaking strength of 100,000pounds-persquare inch; The CrsCz in the sintered composition was in the form" of columnar grains, whereas the Cr4C' was in the form of substantially equi-axed grains.

By pressingthe powder into a billet. having a length manytimes the thickness of the desired article and then severing the billet transversely to form a plurality of the articles as illustrated in Figure 4, articles having substantially the same coeflicient of expansion in all directions are obtained. In other words, the coefiicient of expansion in the direction of the length L, in the direction of the width W, and in the direction of the thickness T are substantially identical when the method illustratedin Figure 4 is employed.

The invention is not limited to the preferred embodimentbut' may be otherwise embodied or practiced within the" scope of the following claims.

I claim:

1. A sintered carbide composition having a coefficient of expansion substantially equal to that of steel, said composition containing by weight about 40% to 60% CrsGz, about 25% to 45% Cr4C, the totalof said' carbides beingbetween about 86% and 90%, the proportion of C13C2 to'GmC being between 1:1 and 7:3, andabout' to' 12% of at least one binder metal of the" group consisting of' nickel and cobalt.

2". A sintered carbide composition, having acoefiicientof expansion substantially equalto that of steel, said" com.- positioncontaining by'weight about 40% to 60%" CrsC2, about to 45 CrrQthe total of said'carhides being between about 86% and'90%, the-proportion of CrzCz to Cr4C being between 1:1 and 7:3, about 10% to 12% of at least one binder metal of the group consisting of nickel and cobalt, and. about 0.5% to. 3.0%. of at least one, grain refining agent of the group consisting of. copper and. tungsten carbide.

3; A sintered carbide composition having, a coefi'icient. of expansion substantially equal to that of steel,. said composition containing by weight about to. 60% CrsC2, about 25% to CnC, the total of said. car.- bides being between about 86% and 90% theproportion ofCrsCz to Cr4C being between. 1:1 and-7:3, about 10% to 12% of at least one binder metal of the. group consisting of nickel and cobalt, and about 0.5% to 2.0%: copper.

4. A. sintered carbide composition having'acoefficient; of. expansion. substantially equal to that of steel, said; composition containing, by weight about. 40.%. to CrsCz, about.25.% t0.45%. (3.116)., the totaliofrsaidcarbides;

4 being between about 86% and 90%, the proportion of CraCato. CriC- being between 1:1 and 7:3,. about 10% to 12% of at least one binder metal of the group consisting of nickel and cobalt, and about 0.5% to 3.0% tungsten carbide.

5. A sintered carbide composition having a coefficient of expansion substantially equal to that of steel, said composition containing by, weight about 40% to 60% CraCz, about 25% to 45 Cr4C, the total of said carbides being between about 86% and 90%, the proportion of CrsCz to CriC being between 1:1 and 7:3, and about 10% to 12% nickel.

6. A sintered carbide composition having a coefficient of expansion substantially equal to that of steel, said composition containing by weight about 40% to- 60% CraCz, about 25%. to 45% r4C,,the total-of saidicarbides being between about 86% and 90%,. the proportion of CrsCz to Cr4C being between 111 and 7:3, about 10% to 12% nickel, and 0.5% to 20% copper.

7. A sintered. carbide composition having a coeflicient of expansion substantially equal to that of steel, said composition containing by weight about 53% CrsCz, about 35%. Cr4C, and about10% to 12% of at leastone binder metal of the group consisting of nickel and cobalt.

8. A sintered carbide composition having a coefficientof expansionv substantially equal to that of steel, said composition containing by weight about 53% CrsCz, about 35% Cr4C, about 10% to 12% of at least one binder. metal of. the group consisting of nickel and cobalt,,and aboutv 0.5%. to, 2.0% copper.

9. A- method of making a sintered carbide composition article having a coefiicient of expansion in all directions substantially equal to that of steel, which comprises providing a powder mixture containing byweight about 40% to 60% CraCz, about 25% to 45 Cr4C, the total. of'said carbides being betweenabout 86% and 90%, the proportion of CrsCz to CrrC being between 1:1 and 7:3, and about 10% to 12% of at least one binder metal of. the group consisting of nickel and cobalt, pressing said mixture into a billet having a length many times the, thickness of the article to be produced therefrom, the pressure being exerted in the direction of the longitudinal axis of the billet, subjecting the billet toa, preliminary. sintering to form. acoherent mass which can be handled. andv shaped, severing the billet transversely into a plurality of articles, and subjecting said articlesto further. sintering at a temperature higher than that. employed in the preliminary sintering in order to form. a strong, article.

10. A method of making a sintered'carbide composition havinga co'efircient of expansion, substantially equalE to that of steel, which. comprises separately forming CrsCz, separately forming Cr4C, mixing the CrsCz, the Cr4C and at least onebinder metal of the group'consisting ofnickel, and'cobalt to'form a batch containing by weight about,40% to 60% CrsCz, about 25% to 45% CrziC, the total of. said carbides being, between about 86% and 90% of the batch, the proportion of? CrsCz to. Cr4C being between. 1:21 and 7:3, and about 10% to-l2% of at least onev of said? binder metals, and pressing and: sintering said batch.

1.1. A method ofmaking a-sintered carbide composition having a coefiicientt of expansion substantially equalto that of steel, which comprises separately forming. Cr3C2 byheating tov reaction temperature a: mixture of chromium oxide and carbon in substantiallystoichio-- metric proportions, to form CrsCz, separately forming, CHC by; heating to reaction temperature. a mixture of. chromium: oxide and carbon in substantially; stoichiometric proportions to form Cr4C, mixing the CrsCz, the, CriC and at least one'bindermetal: of the group consisting of nickel-.andwobalt. togforrrra' batch;containing, by, weight: about 40..%.- to.v 60%; CrsCa. ab.out 25:%; to; 45%: civic?" he"; total: of; said: carbidess. being between about 5 86% and 90% of the batch, the proportions of CrzCz to Cr4C being between 1:1 and 7:3, and about 10% to 12% of at least one of said binder metals, and pressing and sintering said batch.

References Cited in the file of this patent UNITED STATES PATENTS Schroter Sept. 7, 1929 6 Schroter May 6, 1930 Marth May 3, 1938 Wirth July 19, 1938 Comstock June 3, 1941 Goetzel Jan. 1, 1952 FOREIGN PATENTS Great Britain Apr. 18, 1939 

10. A METHOD OF MAKING A SINTERED CARBIDE COMPOSITION HAVING A COEFFICIENT OF EXPANSION SUBSTANTIALLY EQUAL TO THAT OF STEEL, WHICH COMPRISES SEPARATELY FORMING CR3C2, SEPARATELY FORMING CR4C, MIXING THE CR3C2, THE CR4C AND AT LEAST ONE BINDER METAL OF THE GROUP CONSISTING OF NICKEL AND COBALT TO FORM A BATCH CONTAINING BY WEIGHT ABOUT 40% TO 60% CR3C2, ABOUT 25% TO 45% CR4C, THE TOTAL OF SAID CARBIDES BEING BETWEEN ABOUT 86% AND 90% OF THE BATCH, THE PROPORTION OF CR3C2 TO CR4C BEING BETWEEN 1:1 AND 7:3 AND ABOUT 10% TO 12% OF AT LEAST ONE OF SAID BINDER METALS, AND PRESSING AND SINTERING SAID BATCH.
 11. A METHOD OF MAKING A SINTERED CARBIDE COMPOSITION HAVING A COEFFICIENT OF EXPANSION SUBSTANTIALLY EQUAL TO THAT OF STEEL, WHICH COMPRISES SEPARATELY FORMING CR3C2 BY HEATING TO REACTION TEMPERATURE A MIXTURE OF CHROMIUM OXIDE AND CARBON IN SUBSTANTIALLY STOICHIOMETRIC PROPORTIONS TO FORM CR3C2, SEPARATELY FORMING CR4C BY HEATING TO REACTION TEMPERATURE A MIXTURE OF CHROMIUM OXIDE AND CARBON IN SUBSTANTIALLY STOICHIOMETRIC PROPORTIONS TO FORM CR4C, MIXING THE CR3C2, THE CR4C AND AT LEAST ONE BINDER METAL OF THE GROUP CONSISTING OF NICKEL AND COBALT TO FORM A BATCH CONTAINING BY WEIGHT ABOUT 40% TO 60% CR3C2 ABOUT 25% TO 45% CR4C, THE TOTAL OF SAID CARBIDES BEING BETWEEN ABOUT 86% AND 90% OF THE BATCH, THE PROPORTIONS OF CR3C2 TO CR4C BEING BETWEEN 1:1 AND 7:3 AND ABOUT 10% TO 12% OF AT LEAST ONE OF SAID BINDER METALS, AND PRESSING AND SINTERING SAID BATCH. 